Screw-propeller



(Modem 7 E. BENNETT.

SCREW PROPELLER.

No. 345,761. Patented-July 20, 1886.

FIG.2.

FIG.5.

FIGS.

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N PETERS. PholoLilhognphar, Washingwn. D12

UNITED STATES PATENT OFFICE.

EDWIN BENNETT, OF RIO DEJANEIRO, EEAZIL, ASsIeNoE or oNEHALE To RICHARD LAVEEY, OF EoSToN, MASSACHUSETTS.

SC REW-PROPELLER.

SPECIFICATION forming part of Letters Patent No. 345,761, dated July 20, 1886.

Application tiled November 21, 1885. Serial No. 183,576. (ModeL) To all whom it may concern: form part'of this specification, Figure 1 is a Be it known that I, EDWIN BENNETT,asubrear view of the propeller as it appears atject of the Queen of Great Britain, residing at tached to the shaft with portions of three of 5 5 Rio de J aneiro, in the Empire of Brazil, South the blades broken away. Fig. 2 is a top or 5 America, have invented a certain new and plan View, looking downward upon the prouseful Improvement in Screw-Propellers enpeller as it is attached to the shaft. Figs. 3, titled a Differential PitclrScrew Propeller, 4, 5, and 6 are sections of one of the blades. of which the following is a specification. A B O D E F G H, Fig. 1, denote the radii 6') My invention relates to that form of screw at which the sections as represented by.Figs.

IO propeller wherein the angle of pitch varies 3, 4, 5, and 6 are taken.

from thehub to the periphery, and is termed J represents a portion of the shaft; K, the an expanding pitch, also the angle of the hub; L, the nut for securing the propeller on blades varies on the pitch-line. The blades the shaft; M M M M, the four blades of the 65 are deflected backward, to admit of an easier propeller, only one of which is complete, the

i5 motion on entering the water. others are ,shown broken off. The leading The objects of my invention are greater eff1- edge of the blade projects forward at the hub ciency and less vibration to the vessel; and to K, and is represented by the curve A G E G, that end I advance the blade adjoining the Fig. 1. At A, Fig. l, the pitch is greater 7o hub,and make it the leading edge in its spiral than at G, and diminishes outwardly toward 2o path while revolving in the water and prothe periphery.

pelling the vessel ahead, and likewise make The trailing edge of the blade is representthe blade at this same point the greatestpitch. ed by the curve B D F H, Fig. 1. The pitch The blades of the screw, as they project outat B is greater than at D, and gradually di- 7 5 ward from the hub, decrease in pitch until minishes outwardly toward theperiphery also.

25 the periphery is reached, where the pitch is I prefer to make the pitch of the trailing edge least. The-forward edge of the blade at pegreater than the leading edge. riphery is also the last to cut the water in its To illustrate the advantages derived from spiral path. I prefer to make the proportion my propeller, when in operation, the blades 80 of surface of blade to immersed amidshipsecas they sweep through the water in their 0 tion as two is to seven. I prefer to make the spiral path project streams of water backpitch of the screwgreatest at thehub, and gradward at different velocities. The pitches of nally diminish the pitch toward the periphery, the blades being greatest at the center or hub, thereby deflecting the current of water toward the maximum velocity of the current of wa- 8 5 the hub of the propeller, where the combined ter moving backward will be at that point.

5 currents, upon meeting, will react upon each As a resultant, a partial vacunmwill be other and finally be deflected in a direction created, to fill up which a current of water diametrically opposite to the course of the from the periphery will setinward, and therevessel. For example, the screw, when in opby counteract the flow due to centrifugal force. 0 oration, will force the water backward at a \Vhat I claim as my invention, and desire 0 greater velocity at the hub or center of the to secure by Letters Patent, is-

wheel than at the periphery,and thereby form Aserew-propeller with the leading edges of a partial vacuum or vortex at the hub or centhe blades of less pitch at the hub than the ter of the wheel,into which the water from the trailing or after edges of the blades at the hub, 5 outer circle of the wheel (as described by the the pitches of both leading and after edges di- 45 sweep of the propeller-blades) will have a minishing toward the periphery, substantially tendency to rush, and in meeting will react as set forth and specified. upon each other and upon the vessel, after In testimonywhereof Ihavesigned my name which they will take a course directly astern. to this specification in the presence of two IOO The water, in moving in straight lines, will subscribing witnesses.

50 have less tendency to churn or whirl at the WVitnesses: EDWIN BENNETT.

periphery of the screw. O. G. S. SHALDERS,

Referring to accompanying drawings, which 0. G. ANDREWS. 

